This invention is concerned with methods of manufacturing moulded articles of glassware and with mould portions for use in such manufacture.
The manufacture of moulded articles of glassware frequently involves a necessity to cool the mould used either during a moulding operation or between successive moulding operations. For example, in the manufacture of glassware by a glassware forming machine of the individual section type, gobs of molten glass are delivered successively to moulds in which the gobs are formed into parisons and subsequently to further moulds in which the parisons are formed into finished articles. The moulds of a machine of the individual section type absorb heat from the glass at a rate which is faster than the heat can be dissipated without the provision of cooling means for the moulds. Where it is necessary to provide such cooling around a mould cavity of the mould, it is known to provide a plurality of cylindrical cooling passages in the mould distributed around the mould cavity and to pass cooling fluid through these passages so that the cooling fluid absorbs heat from the mould and carries it away. The cooling effect can be varied around the mould cavity by controlling the supply of cooling fluid to each passage independently. U.K. Patent Specification No. 1533622 describes such an arrangement. In such cooling arrangements, the cooling effect achieved is influenced by the velocity of the air, its degree of turbulence and the temperature difference between the air and the wall of the passage. The cooling effect, therefore, is greatest in an entrance portion of the passage where the turbulence and temperature difference are greatest and progressively decreases along the length of the passage. This progressive decrease in cooling effect is disadvantageous in cases where the maximum cooling effect should ideally be in the central portion of the cooling passage. For example, where a bottle-shaped article is being moulded, the mould comprises an end portion into which the mould cavity does not extend and which does not require much cooling, a central portion in which most of the mould cavity is formed and which requires the most cooling as it contains the most molten material, and an opposite end portion in which a neck portion of the mould cavity is formed and which requires less cooling than the central portion because it contains less molten material. The cooling passages extend through the end portions as well as through the central portion so that, in order to achieve sufficient cooling in the central portion, at least one of the end portions has to be cooled more than is desirable because the concentration of the cooling effect at the entrance. Attempts have been made to concentrate the cooling effect where desired by inserting a tube made of insulating material into an entrance portion of each cooling passage to reduce the cooling effect in the entrance portion and therefore increase it in other portions of the passage. The above mentioned U.K. Patent Specification No. 1533622 describes the use of such insulating tubes. This, however, is only a partial solution to the problem which is also inconvenient as the tubes must be secured in position. Furthermore, the presence of the insulating tubes, reduces the available area for fluid flow and thereby increases the resistance to flow along the passage.
It is an object of the present invention to provide a method of manufacturing moulded articles in which the mould is cooled by cooling fluid flowing along a cooling passage in the mould and the cooling effect is concentrated without the use of an insulating tube.